Speaker cabinet enclosure and method of making same

ABSTRACT

A speaker cabinet enclosure comprising a rectangular parallelepiped having a speaker unit in its front wall, a layer of insulation on each of its top, base and sidewalls, and a rear wall in which two sets of a plurality of apertures are disposed, each such set being a mirror image of the other in nature and disposition. Insulation is provided against the speaker unit frame above and below its magnet. A layer of insulation is provided directly behind the magnet of the speaker unit, and additional layers of insulation may be provided therebehind.

United States Patent 2,766,839 10/1956 Baruch et al 3,135,349 6/1964Lahti 181/31 2,515,031 7/1950 Black,.lr 179/115.5 FOREIGN PATENTS1,065,126 12/1953 France 181/31 820,307 9/1959 Great Britain. 181/31102,888 12/1937 Australia 181/31 Primary Examiner-Stephen J. TomskyAttorney-Frank R. Zugelter ABSTRACT: A speaker cabinet enclosurecomprising a rectangular parallelepiped having a speaker unit in itsfront wall, a layer of insulation on each of its top, base andsidewalls, and a rear wall in which two sets of a plurality of aperturesare disposed, each such set being a mirror image of the other in natureand disposition. insulation is provided against the speaker unit frameabove and below its magnet. A layer of insulation is provided directlybehind the magnet of the speaker unit, and additional layers ofinsulation may be provided therebehind.

a! a Q i :ZL Zfl/ BACKGROUND OF THE INVENTION 1. Field of the invention1 The field of art to which the invention is most likely to pertain isgenerally located in the class of apparatus relating to speakers. Class181, Acoustics, U.S. Patent Office classification, appears to be theapplicable general area of art in which the claimed subject matter ofthe type involved here has been classified in the past.

2. Description of the Prior Art Loud speaker apparatuses, of the typeinvolved here, are disclosed in US. patents classified in said Class 18I.

SUMMARY An object of this invention is to cabinet enclosure.

Another object of this invention is to provide for sound propagation ofdesired frequencies from within its chamber to the exterior of thecabinet, the desired frequencies being those of which the responsecurves of sound propagated forwardly from a speaker cone are shown to beweak.

Another object of this invention is to provide for optimum evenness ofbackloading on the speaker cone resulting in optimum clarity of soundreproduction (transient response).

.A further object of the invention is to provide for evenness ofbackloading of a speaker cone which will permit its operation at highervolume (watts) without corresponding increase in distortion ordestruction of the speaker unit.

A further object of the invention is to provide for a novel speakercabinet enclosure having an uncomplicated structure and in which amaximum evenness of backloading of the speaker cone is established, theresult of which is excellent transient response.

Another object of the invention is to provide for the flattest possiblefrequency response by controlling the frequencies or frequency rangespropagated from the chamber of the cabinet to the exterior of thecabinet by means of novel structure in the rear wall of the cabinet. Thefrequencies or their ranges propagated through the rear wall are thosefrequencies which the response curves of the sound propagated from theforward direction of the speaker cone are shown to be weakv Anotherobject of this invention is to provide for a cabinet of relativelyinexpensive, simplified and efficient construction.

Another object of this invention is to provide for faithful and clearreproduction of sound.

Another object of this invention is to provide a novel method forestablishing clear and faithful reproduction of sound in and from acabinet enclosure constructed on a bass reflex principle.

Another object of this invention is to provide for the reduction in sizeof a bass reflex cabinet over the sizes normally associated with suchtype cabinets, by application of two features involving the cabinetport, namely, the distribution of apertures to obtain even backloadingof the speaker cone and. choice of diameters of apertures to controlfrequency response of the sound propagated in the interior ofthe cabinetthrough the rear wall to the exterior of the cabinet.

These and other objects and advantages of this invention will becomemore apparent by a full reading of the following description, claimsappended thereto and drawings comprising two sheets.

provide fora novel speaker BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is aperspective view ofa speaker cabinet enclosure, broken away to showelements of the device embodied in the invention.

FIG. 2 is a view taken on line 2-2 of FIG. 1.

FIG. 3 is a view taken on line 33 of FIG. 2, but with foldedover layersofinsulation removed.

FIG. 4 is a view taken on line 4-4 of FIG. 2, and drawn to scale for thepreferred embodiment.

FIG. 5 is a modification ofa novel rear wall embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring 'now to the drawing inwhich reference characters correspond to like numerals in the followingdescription, 10 (FIG. I represents generally a speaker cabinet enclosureembodying my invention. Enclosure 10 comprises a cabinet 12 ofrectangular parallelepiped construction forming an acoustical cavity orchamber 13. Cabinet 12 comprises a pair ofopposing spaced sidewalls I4and .16, a front wall I8, a rear wall 20, a top wall 22, and a bottom orbase wall 24. Cabinet 12 is formed from thin boards, plywood or othersuitable material known for its utility in the production of speakerenclosure cabinets. Each of the sidewalls l4, 16, top wall 22 and base24 is recessed as at 26 FIGS. 1 and 2) along their vertically andhorizontally disposed edges, as the case may be, adjacent front walll8and rear wall 20, so as to produce shoulders 28 against which frontand rear walls 18, 20 abut upon assembly of cabinet 12, therebyproviding for a flushjuncture of the exterior faces of walls 18, 20 withsuch edges of sidewalls l4, 16, top wall 22 and base 24. A grille cloth(not shown) may be mounted upon front wall 18 and molding (not shown)applied to the front wall thereafter for providing an artistic orstylish appearance to cabinet 12 as a whole.

A wooden bar or strip 30 or the like is mounted along each interiorjuncture of top and bottom walls 22, 24 with sidewalls l4 and 16, asshown in FIGS. 1 and 3. Means, such as nails (not shown), secure each ofbars 30 to walls 14, 16, 22, 24, as the case may be. Means, such as aplurality of screw holes, are provided in rear wall 20 for registeringupon shoulders 28 whereby wood screws 32 secure rear wall 20 to theside, top and base walls of cabinet 12. Means, such as ring shank nails33, tack and secure front wall 18 to such walls.

Front wall I8 is provided with an opening 34 about which a frame 35 ofaspeaker unit 36 is suitably secured to wall 18 by mounting screws 37(FIG. 2). A layer ofinsulation 38, such as fiber glass, is mounted tothe interior face of each of sidewalls l4, 16, top wall 22and base 24.Each of a pair of insulating layers 39 is folded over on itself anddisposed above and below a magnet 40 secured in conventional fashion toframe 35 to substantially fill the volume between the speaker frame andthe plane coincident with the back of magnet 40, as clearly shown inFIG. 2. Layers 39 extend laterally to layers 38 mounted on sidewalls I4,16. A layer of insulation 38 is vertically mounted directly behindmagnet 40 of speaker unit 36 and extends coextensively with the heightand width of chamber 13 as defined by layers 38 mounted on sidewalls 14,16, top wall 22 and base 24. In this preferred embodiment havingparticular dimensions as set forth hereinafter, additional layers ofinsulation 38", similar to layer 38', are provided behind layer 38' andextend to rear wall 20. However, it should be understood that the numberof additional layers of insulation 38" need not extend completely torear wall 20, as it is a matter of preference as to the degree of soundreverberation one desires to hear emanating from chamber 13 of cabinet10.

A pair of holes 52 (FIG. 4) is provided in rear wall 20 whereby leadwires 53 (FIG. 3) conventionally secured to speaker unit 36 may besecured to a barrier terminal strip 54 (shown in phantom) secured to theexterior face of rear wall 20. Suitable electrical wiring (not shown)from strip 54 to a tuner, amplifier or the like is utilized foroperation of enclosure 10.

The portions of sidewalls l4, 16, top wall 22 and base wall 24 joiningeach other, as the case may be, are mitered, and with the describedsecurement of front and rear walls 18, 20 to such walls, provides anefficient, snug and airtight construction.

Assembly of cabinet [2 should be apparent fromthe foregoing description.

Sets or patterns of apertures 45, 46 are provided in rear wall 20. HO. 4shows that each set or pattern of apertures 45, 46 is disposed in itscorresponding half of rear wall 20 so as to be a mirror image orreflection of the other set or pattern of apertures in the other half ofrear wall 20. 7

Each aperture 47 therein isof a diameter so that the total spatial areaofthcse apertures is equal to the spatial area for a port or openingutilized in a cabinet enclosure constructed on the bass rellexprinciple. The distribution of apertures 47, Wlllt'll involves location,distance between and number of such apertures, are so chosen as toprovide a maximum evenness of but ltltiiltllllt" on cone 49 of speakerunit 35, thereby obtaining maximum clarity of sound and consequentlymaximizing transient response.

'aliinet I2 is constructed on the bass reflex principle and incorporatestherein the novel feature of sets or patterns of apertures 45, 46 inrear wall 20 whereby clear and faithful reproduction of sound isattained. The method for determining given sets or patterns comprisesgenerally the following steps:

l. Establishing a spatial area of a conventional port for a bass reflexcabinet.

2. Determining the pattern(s) or distribution of apertures to obtaineven backloading on the speaker cone.

3. Determining the diameters of apertures 47 which will permit thedesired frequencies or frequency ranges to pass to the exterior of thecabinet via the apertures.

To effect step 1., it is first to be noted that the spatial area of theport included therein is related to the free air resonancecharacteristic of the speaker unit mounted in the bass reflex cabinet.First constructing a cabinet A having the estimated port spatial areaand a cabinet B having a spatial area larger than that of Cabinet A, A-Blistening comparisons are made to determine which cabinet decreases thefree air resonance peak in the most pleasing manner. If cabinet A soundsbetter than Cabinet B, the port spatial, area in cabinet B will be madesmaller than that in cabinet A and the AB listcning comparison isrepeated. Adjustments of the port spatial areas are repeated until theflattest response in the bass frequency range is obtained.

In regard to step 2., each of two rear walls 20 is perforated throughouttheir areal dimensions with a plurality of apertures 47. The aperturesare generally formed on a geometrical pattern, say, such as involvingrectangular, square, triangular or circumferential or circular'patterns,or the like. The total spatial area developed in each rear wall 20 isgreater than the indicated equivalent spatial area from step I.Different patterns of apertures 47 in each of rear walls 20 isestablished by filling excess apertures with corks. The effectiveness ofthe pattern of patterns in cabinet A is compared with the effectivenessof the pattern or patterns in cabinet B by A-B listening comparisons.The pattern is changed in the cabinet which yields the least clarity.Then another listening comparison is made. This process is repeateduntil the reproduction of sound is the clearest possible (transientresponse has been optimized) by the evenness of backloading of thespeaker cone 49.

To carry out step 3., the cabinet, chosen to be the optimum constructionfor steps 1. and 2., is tested for overall flatness of frequencyresponse. If the frequency response is satisfactory, no furtheradjustments of the diameters of the apertures are required. However, ifpeaks or valleys exist in the overall frequency response, then step 3.is performed. Each of two rear walls 20 of cabinets A and B; havingsubstantially the same pattern of apertures 45, 46, but the apertures ineach cabi'netA, B having different diameters, are compared by A-Blistening tests. The initial choice of change in diameters in cabinet Awith respect to cabinet B is estimated by the following. If there is toomuch bass response, the diameters of the apertures in cabinet B are madelarger with a corresponding decrease in number of apertures in order tomaintain the same port spatial area as determined in step 1. If there istoo much high frequency response, the diameters of the apertures incabinet B are made smaller with a corresponding increase in number ofapertures in order to maintain the same port spatial area as determinedin step 1. The diameters of the apertures in cabinet B are made largeror smaller, maintaining the same spatial area until the flattestpossible overall frequency response is obtained. It is to be understoodthat the plurality of apertures 47 may include different diameters inorder to satisfy the need for flat overall response.

Additional cabinets 12 which are constructed using the same dimensionsin all details and speaker units 36 having the same characteristics willsound substantially identical.

An example of the dimensions and cltaructeristies of preferredembodiment 10 is as follows:

Length: 11 Width: 8% Depth: 7%

(These are outside dimensions of cabinet, without mo mg.

Walls: plywood Speaker unit: Oaktron 69FEUW, manufactured by OaktronIndustries, Inc., Highway 69 South Monroe, Wisconsin 53566. Unitcentrally mounted on center line C pass'ng through front and rear walls18, 20 (FIG. 1).

Wiring: Conventional Diameter of apertures: 31,-,

Number ofapertures: 30, subdivided into two groups of 15 each, in arectangular pattern 3 x 5, each pattern substantially equally spaced inrespective halves of the rear wall of cabinet, divided about line D inFIG. 4 to form mirror.

Centers of apertures:

'70 in FIG. 4).

Insulation: Each layer essentially 1 inch thick fiber glass, withinsulation 38 comprising 2 layers.

Opening 34: an oval configuration, having M inch smaller dimensions thanthe maximum dimensions of the cone.

inch (see reference character FlG. 5 illustrates a modification of theinvention as believed applied to an enclosure having equal dimensions oflength and width and a round speaker unit 136. A cabinet 112 isconstructed and assembled in accordance with the above description.Round speaker 136 having a magnet 140 is secured to its front wall (notshown). Rear wall is believed to demon strate a pattern or patterns bywhich even backloading of a cone ofa round speaker unit 136 is obtained.

The pattern or patterns of apertures 145, I46 and 148 is duplicated ineach quadrant M, N, P and R imposed upon rear wall I20 as shown. Amirror image pattern of such apertures about each half of each diagonalS, T in their respective quadrants can be established in accordance withthe above outlined steps.

It should be apparent now that a change in distribution of apertures I47in one of such quadrants M, N, P and R necessitates a correspondingchange in each of the other remaining quadrants in order to maintaineven backloading on the cone of speaker unit I36. The inventive conceptof this invention extends to variations of the configurations ofapertures 47 and 147 and such configurations are not limited to thecircular configurations thereof illustrated in the drawing. Suchvariations include (FIGS. 69) squares 157, rectangles 158, triangles159, ovals 160, and other geometrical configurations suitable forcarrying out the objects and purposes of the inventron.

Pursuant to the requirements of the-patent statutes, the principle ofthis invention has been explained and exemplified in a manner so that itcan be readily practiced by those skilled in the art to which itpertains, such exemplification including what is presently considered torepresent the best embodiment ofthe invention.

Therefore, what I claim as patentably novel is:

l. A speaker cabinet enclosure including front, rear, side, base and topwalls comprising in combination a bass reflex cabinet having an acousticchamber and including a full range speaker unit and magnet therewithcentrally mounted on the front wall,

a layer of insulation mounted on the interior face of each sidewall, topwall and base of said cabinet,

oval in nature.

unit and filling substantially the volume of the chamber between theframe of the speaker unit and a plane coincident to the back end ofsaidmagnet,

at least one layer of insulation abutting the rear end of said,

unit and extending substantially laterally and vertically of the chamberof said cabinet, and at least two patterns of apertures in said rearwall, the distribution of which is generally geometrically formed aboutthe central axis of said speaker unit but without substantially acylinder generatedby the areal dimensions of the magnet of said speakerunit, whereby even backloading upon the cone of said speaker unit isachieved for all frequencies reproduced by said full range speaker unit.2. The improvement of claim 1 in which said apertures arc circular. v

3. The improvement of claim 2 in which each of said apertures is of thesame diameter as the other apertures.

4. The improvement of claim 1 in which said apertures are rectangular innature.

5. The improvement of claim 1 in which said apertures are 6. Theimprovement of claim 1 in which said apertures are triangular in nature.

7. The improvement of claim 1 in which said apertures are square innature. 1

8. An improved speaker cabinet enclosure of relatively small size andwhich forms a bass reflex cabinet type of enclosure, such enclosureincluding the combination of a full-range oval speaker unit and magnettherewith centrally mounted on the front wall of said cabinet, a layerof insulation mounted on the interior face of each wall of said cabinet,layers of insulation filling substantially the volume in the chamberabove and below said magnet, such filling being limited between a planecoincident to the back end of said magnet and the frame of said speakerunit, at least one layer of insulation abutting the rear end of saidunit and extending substantially laterally and vertically in 6 thechamber of said cabinet, and

patterns of apertures formed in the rear wall substantially in the upperand lower areas in said wall, the distribution of which is geometricallyformed about the central axis of said speaker unit but substantiallywithout a cylinder generated by the areal dimension of the said magnet,

whereby even backloading upon the cone of said speaker unit is achievedfor all frequencies reproduced by said full-range speaker unit.

9. A method for providing clarity of sound by evenly backloading thecone of a full-range speaker unit centrally mounted on the front wallol'a bass reflex cabinet enclosure of a given size comprising the stepsof l. forming a port opening having the required spatial area in a rearwall of an enclosure of the same size, such opening producing theflattest overall response in the bass frequency range for the enclosure,and

2. perforating a rear wall of another enclosure of the same size with apattern and distribution ofa plurality of apertures whose total spatialarea is equivalent to the required spatial area in the first mentionedenclosure.

10. A method for providing clarity of sound by evenly backloading thecone of a full-range speaker unit centrally mounted on the front wall ofa bass reflex cabinet enclosure of a given size and for providing thewidest and flattest response for said full-range speaker unit,comprising the steps of l. forming a port opening having the requiredspatial area in a rear wall of an enclosure of the same size, suchopening producing the flattest overall response in the bass frequencyrange for the enclosure,

2. perforating a rear wall of another enclosure of the same size with apattern and distribution of a plurality of apertures whose total spatialarea is equivalent to the required spatial area in the first mentionedenclosure, and c angmg the areal size of one or more of the apertures insaid plurality by which the flattest and widest possible frequencyresponse is obtained, a corresponding change in number of aperturesbeing made to maintain the required spatial area developed in saidforming step.

1. A speaker cabinet enclosure including front, rear, side, base and topwalls comprising in coMbination a bass reflex cabinet having an acousticchamber and including a full range speaker unit and magnet therewithcentrally mounted on the front wall, a layer of insulation mounted onthe interior face of each sidewall, top wall and base of said cabinet,layers of insulation disposed above and below said speaker unit andfilling substantially the volume of the chamber between the frame of thespeaker unit and a plane coincident to the back end of said magnet, atleast one layer of insulation abutting the rear end of said unit andextending substantially laterally and vertically of the chamber of saidcabinet, and at least two patterns of apertures in said rear wall, thedistribution of which is generally geometrically formed about thecentral axis of said speaker unit but without substantially a cylindergenerated by the areal dimensions of the magnet of said speaker unit,whereby even backloading upon the cone of said speaker unit is achievedfor all frequencies reproduced by said full range speaker unit.
 2. Theimprovement of claim 1 in which said apertures are circular. 2.perforating a rear wall of another enclosure of the same size with apattern and distribution of a plurality of apertures whose total spatialarea is equivalent to the required spatial area in the first mentionedenclosure, and
 2. perforating a rear wall of another enclosure of thesame size with a pattern and distribution of a plurality of apertureswhose total spatial area is equivalent to the required spatial area inthe first mentioned enclosure.
 3. The improvement of claim 2 in whicheach of said apertures is of the same diameter as the other apertures.3. changing the areal size of one or more of the apertures in saidplurality by which the flattest and widest possible frequency responseis obtained, a corresponding change in number of apertures being made tomaintain the required spatial area developed in said forming step. 4.The improvement of claim 1 in which said apertures are rectangular innature.
 5. The improvement of claim 1 in which said apertures are ovalin nature.
 6. The improvement of claim 1 in which said apertures aretriangular in nature.
 7. The improvement of claim 1 in which saidapertures are square in nature.
 8. An improved speaker cabinet enclosureof relatively small size and which forms a bass reflex cabinet type ofenclosure, such enclosure including the combination of a full-range ovalspeaker unit and magnet therewith centrally mounted on the front wall ofsaid cabinet, a layer of insulation mounted on the interior face of eachwall of said cabinet, layers of insulation filling substantially thevolume in the chamber above and below said magnet, such filling beinglimited between a plane coincident to the back end of said magnet andthe frame of said speaker unit, at least one layer of insulationabutting the rear end of said unit and extending substantially laterallyand vertically in the chamber of said cabinet, and patterns of aperturesformed in the rear wall substantially in the upper and lower areas insaid wall, the distribution of which is geometrically formed about thecentral axis of said speaker unit but substantially without a cylindergenerated by the areal dimension of the said magnet, whereby evenbackloading upon the cone of said speaker unit is achieved for allfrequencies reproduced by said full-range speaker unit.
 9. A method forproviding clarity of sound by evenly backloading the cone of afull-range speaker unit centrally mounted on the front wall of a bassreflex cabinet enclosure of a given size comprising the steps of
 10. Amethod for providing clarity of sound by evenly backloading the cone ofa full-range speaker unit centrally mounted on the front wall of a bassreflex cabinet enclosure of a given size and for providing the widestand flattest response for said full-range speaker unit, comprising thesteps of
 1. forming a port opening having the required spatial area in arear wall of an enclosure of the same size, such opening producing theflattest overall response in the bass frequency range for the enclosure,